Personal computer (PC) marketing surveys show that one of the most common customer requests for a PC manufacturer is faster PC startup. Currently, most PCs are pre-loaded with Windows operating system (OS) and application software programs. Typically 1.5 to 2 minutes are needed to complete a full boot process from a Power-Off state (S5 in Advanced Configuration and Power Interface (ACPI)). When an anti-virus software is running, the full boot startup process may be longer.
Windows Vista currently offers the Sleep mode (S3 in ACPI), Hibernate mode (S4 in ACPI), and Hybrid-Sleep mode power management features. These power management features allow PCs to resume quickly to the last state before power-off, each offering different power consumption level, resume time, and stability. For example, the S3 Sleep mode saves data (such as the last system state context data) in a system memory and places the system in a stand-by mode. The computer system can be woken up and used almost immediately. However, in the S3 Sleep mode, the power must not be turned off. Once out of power, the system will have to start again using a full boot process from the S5 Power-Off state.
The S4 Hibernate mode saves data (such as the last system state context date) in a hard disk drive as opposed to the system memory. When the computer system needs to be used again, the system boots up using the last system state context data. Boot up from the S4 Hibernate mode takes longer than from the S3 Sleep mode.
These power management features all consume power even when the PC is not in use. In addition, with the exception of the S4 Hibernate mode, these power management features do not work if a user turns off the PC or unplugs the PC's power cord. While the S4 Hibernate mode works if a laptop power cord is unplugged, the battery power consumption of the S4 Hibernate mode is still higher than the S5 Power-Off state.